Multidisciplinary study of flash floods in the Caldera de Taburiente National Park (Canary Islands, Spain)

The national parks of the Canary Islands have specific environmental features that attract thousands of tourists every year. Most of the parks are located in mountainous areas, where hydrogeomorphic processes and their related hazards are frequent. The main aim of this study is to improve our understanding of the effects and frequency of these processes in an ungauged river basin located on the island of La Palma. In this river basin, the use of hydrological and hydraulic modelling based on classic data sources and flood risk analysis methods has important shortcomings because of a lack of or incomplete information. Here, we use palaeohydrological data from tree-ring analyses of disturbed trees as these appear to be the only reliable alternative. In addition, dendrogeomorphological data are compared with available meteorological and documental information to develop a multidisciplinary flash flood record. This is the first time that Pinus canariensis has been used in a dendrogeomorphological study we assess its suitability for the reconstruction of flash flood events. Such techniques have not been applied before in subtropical, tropical or equatorial areas. Tree-ring dating data were mostly obtained from 63 wounds from 54 trees from which two main types of post-damage tree response were identified: growth release and growth suppression. Injuries occurring in 1962 were especially relevant (affecting almost all the older trees) and also in 1997, with both presenting a large number of replications. Other injuries occurred in 1993, 2001, 2003, 2007 and 2009, obtaining a record from the dendrogeomorphological evidence. The data were compared with daily meteorological data and available documental sources in order to establish the most complete flash flood record possible. Our findings provide new insight into past flood events, their frequency-magnitude relationships, and climatic triggers, that can provide park managers with tools to reduce natural risks and their effects on visitors and infrastructure.